| absolute threshold | minimum stimulation needed to detect a particular stimulus 50% of the time. (p.195) |
| accomodation | adapting one's current understandings (schemas) to incorporate new information. (p.143) |
| acetycholine | (ACh); neurotransmitter that triggers muscle contraction. (p.62) |
| achievement test | test designed to assess what a person has learned. (p.432) |
| acoustic encoding | encoding of sound, especially the sound of words. (p.350) |
| acquisition | initial stage in classical conditioning; phase associating a neutral stimulus with an unconditioned stimulus so that the neutral stimulus comes to elicit a conditioned response. In operant conditioning, the strengthening of a reinforced response. (p.314) |
| action potential | a neural impulse; a brief electrical charge that travels down an axon. The action potential is generated by teh movement of positively charged atoms in and out of channels in the axon's membrane. (p.159) |
| adrenal glands | a pair of endocrine glands just above the kidneys. The adrenals secrete the hormones epinephrine (adrenaline), and nonepinephrine (nonadrenaline), which help to arouse the body in times of stress. (p.95) |
| aggression | any physical or verbal behavior intended to hurt or destroy. (p.719) |
| algorithm | a methodical, logical rule or procedure that guarantees solving a particular problem. Contrasts with the usually speedier (but more error-prone) use of heuristics. (p.387) |
| alpha waves | the relatively slow brain waves of a relaxed, awake state. (p.272) |
| altruism | unselfish regard for the welfare of others. (p.735) |
| amnesia | loss of memory (p.358) |
| amygdala | two almond-shaped neural clusters that are components of the limbic system and are linked to emotion (p.74) |
| aphasia | impairment of language, usually caused by left hemisphere damage either to Broca's area (impairing speaking) or to Wernicke's area (impairing understanding). (p.82) |
| applied research | scientific study that aims to solve practical problems. (p.13) |
| aptitude test | a test designed to predict a person's future performance. (p.432) |
| aptitude | capacity to learn. |
| assimilation | interpreting one's new experience in terms of one's existing schemas. (p.143) |
| associative learning | learning that certain events occur together. The events may be two stimuli (classical conditioning) or a response and its consequences (operant conditioning.) (p.309) |
| motivation | the psychological feature that arouses an organism to action toward a desired goal |
| instinct | inborn pattern of behavior often responsive to specific stimuli |
| hierarchy of needs | Maslow's pyramid of human needs, beginning at the base with physiological needs that must first be satisfied before higher-level safety needs and then psychological needs become active |
| neuron | a cell that is specialized to conduct nerve impulses |